The long range objective of this project is to develop high resolution MRI into an effective clinical tool for the management of breast cancer. While MRI is unlikely to play a role in general screening for breast cancer, a powerful role may exist for MRI in providing anatomic and biologic staging information that can be used to elucidate problem cases, to stage the extent of disease prior to surgery, to decide treatment strategies and to monitor treatment response. We have a unique opportunity with the collaborative nature of our breast MRI program and a team of breast cancer clinicians and researchers to determine where MRI might play a useful role in the management of breast cancer and to expedite the transition from research to clinical practice. Preliminary results in a subset of patients with primarily late stage breast cancer demonstrate that the high resolution imaging and analysis technique (TARGET) developed by the investigators is highly accurate m anatomic staging and can potentially stratify breast pathologies in-vivo. The first specific aim of this proposal is to determine the diagnostic specificity of TARGET imaging and to extend the evaluation of anatomic and biologic staging accuracy to include a broad spectrum of breast pathologies. The second specific aim will explore TARGET's ability to characterize and distinguish stages in breast disease progression and to measure an early response to therapy in a transgenic mouse model of human breast cancer. The line selected has been shown to develop stochastic, focal tumors in the mammary gland in the presence of a fully functional immune system. This model will provide an opportunity to observe the progression of breast disease with MRI and to investigate the histopathologic basis for changes measured by MRI during therapy. The mice studies will lead to studies using TARGET in clinical trials to evaluate new biotherapies in humans. The third specific aim focuses on technological developments needed in order for breast MRI to be used practically in a clinical setting. These will include image analysis and display capabilities for quick review and assessment of breast MRI data and ultimately for use with a dedicated imaging and breast biopsy magnet system presently under development. As part of the goal to facilitate the translation to clinical usage, a teaching library of cases representing the full spectrum of breast disease, including the normal breast, will be created and made available to breast cancer clinicians and researchers, residents, fellows and faculty. It is expected that this resource will contribute to our increased knowledge and understanding of breast cancer.